The primary aim of this proposal is to confirm and to test the generalizability of the link between self produced locomotor experience and psychological development. Through converging research operations that take advantage of ecologically, culturally, orthopedically, and neurologically mediated variations in motor development, we plan to test whether the emergence of wariness of heights and the ability to use periperherai optical flow in the control of posture are brought about by locomotor experience or merely correlated with such experience. We also plan to test an important account of developmental process - namely, that locomotor experience orchestrates the development of wariness of heights by refining the infant's ability to use peripheral optical flow for postural control. We will test the generalizability of the link between responsiveness to peripheral optical flow and wariness of heights on three separate groups of 40 infants: African Americans (who are likely to be precocious in the onset of locomotion) and Hispanics and Asian Americans (who are likely to be delayed in the onset of locomotion). Responsiveness to peripheral optical flow in a moving room and wariness of heights on a visual cliff are expected to be positively correlated, though if age is a mediating factor, the relation should be attenuated in the precocious crawlers and enhanced in the delayed crawlers. In subsequent age-held-constant experiments, we plan to compare 20 locomotor and 20 prelocomotor infants on a new paradigm designed to assess infant postural compensation to peripheral optical flow and a new paradigm designed to more sensitively assess wariness of heights. There is an overarching theoretical point to be investigated in the proposed studies--the principle of probabilistic epigenesis (Gottlieb, 1983)--which states that one developmental acquisition produces experiences that bring about a host of new developmental changes in the same and different domains. The point of our research plan is to quantify the role of locomotor experience on psychological development; the theoretical im plication of our work is that of highlighting the potential importance of motodc activity broadly considered (eventually including visual scanning, reaching, and walking) on human development; and the clinical and mental health relevance of our work is its potential diagnostic and therapeutic application to children with motoric delays.